While there have been a number of movies (not to mention novels, manga, kabuki, and bunraku) based on Chushingura, there has never really been a single, definitive version, and none that could be called pillars of Japanese cinema (the Mizoguchi version is perhaps the best known). Seven Samurai was an original story, and one of the greatest things ever filmed, period.

Did I hallucinate viewing a version with Toshiro Mifune that blew the top of my head off? I saw it when I was a kid. Wikipedia mentions it as well. There was a 1962 version with Mifune, but it wasn't outstanding, and certainly wasn't directed by Kurosawa (who never did a version of Chushingura).
Top Ten Films 1930-2009. 2014 1.